Acetals are polymers of formaldehyde which are technically known as polyoxymethylenes. Heretofore, these thermoplastic polymers have been used extensively in various injection molding and tubing applications. In particular, acetals have been used in the automotive industry to make molded automobile parts ranging from door handles to fuel tank caps. In addition, the housing components of current fuel filter assemblies are typically made from acetal.
Other automobile components which may be made from acetal are the subject of various patents such as U.S. Pat. No. 4,114,130 which discloses an acetal casing for a float operated fuel level sender; U.S. Pat. No. 4,305,416 which discloses a back-up fuel tank composed of polyacetal; U.S. Pat. No. 5,049,271 which discloses a fuel tank filter having a solidly constructed separator made from acetal resin to hold the porous filter toward the bottom of the tank; and U.S. Pat. No. 5,085,768 which discloses a fuel tank having a plastic magnet formed by adding a magnetic powder to an acetal resin.
In addition to having high load bearing and excellent durability characteristics, acetals generally have excellent physical properties for filtration. Some of these properties are noted in U.S. Pat. No. 3.568,846 which relates to an improved filter media prepared from discrete particles of plastic material having irregular, nonuniform shaped surfaces. The plastic materials include such materials as polyoxymethylenes, also known as polyacetals.
Fuel filters are commonly employed in vehicular fuel systems to separate any undesirable contaminants from the fuel required for the operation of the vehicle's engine. Most, if not all, fuel filters today use some type of fabric within the fuel filter to preclude flow of any unfiltered fuel into the engine which could subsequently damage the engine.
Woven fabrics of various compositions have long been known and used in fuel filters. For example, U.S. Pat. No. 4,961,850 discloses the use of woven threads of nylon or Saran, a polyvinylidene chloride thermoplastic polymer and a trademark of the Dow Chemical Company. In that patent, the woven fabric was used in an in-tank fuel filter to filter gasoline in the vehicular fuel system.
However, none of the present compositions of fabric have been able to meet the stringent requirements for flex fuel filtration in vehicles such as automobiles. While most, if not all, of the present compositions for fuel filter fabrics perform well in conventional fuel systems which use gasoline as the fuel, the same cannot be said for those same compositions and fuels filter fabrics where alternative fuels are used in the fuel system.
Specifically, alternative fuels such as methanol, ethanol, and grain alcohol are rapidly being developed for use in vehicular fuel systems. However, these alternative fuels cause the currently developed fabrics used in the fuel filters to swell and starve the engine of fuel.
Thus, a need exists liar a fuel filter fabric which can readily be welded to the housing component of the fuel filter, and whose monofilaments or fibers will not be affected by the presence of alternative fuels, so as to starve the engine of fuel or allow a contaminant to pass through the fuel filter.